In recent years, a digital color copy machine which has superior color reproducibility and therefore can provide a reproduced image extremely close to its original is manufactured, that is the fruit of years of a technological development. There is concern, however, that this superior digital color copy machine is likely to be illegally used in the forgery of paper money, valuable securities and the like.
Generally, it is a digital color copy machine that is used in forgery. Therefore, a digital color copy machine provided with a mode to prevent forgery (“forgery prevention mode”, hereinafter) as a countermeasure is commercially available today. The digital color copy machine having the forgery prevention mode has such an arrangement as to pre-scan an original document when it is set on a document table, and when judging that the document thus set is identical with a specific document registered in a device in advance, prohibit the execution of image formation for this document, or permit the execution of image formation provided that the output image is given a particular process, such as a process to attach a particular pattern for tracking use, or deformation processes including a variable magnification process, an oblique face process, a mirror image process, and the like, so as to prevent accurate image formation.
As discussed, the forgery of a specific document commonly involves the use of a digital color copy machine. Consequently, the use of an image transmission device for forgery purposes, for example, forging a specific document by faxing a document, has been overlooked.
However, as color facsimiles have been popularized, and scanners, image processing and printing techniques have been improved, the use of an image display device, such as a facsimile in forgery would be anticipated in near future. Therefore, there is growing concern that, in addition to paper money and valuable securities, those requiring careful attention in terms of copying, such as a season ticket, a commutation ticket, and the like, and copyright works are transmitted by such image transmission devices as a facsimile and a network-connected personal computer, so as to be used for forgery at a receiving end.
Further, Japanese Unexamined Patent Publication No. 130657/1996 (Tokukaihei 8-130657 published on May 21, 1996) discloses a facsimile which prohibits transmission of an image with respect to a designated destination in the case where the image of a transmission document is a special one. Namely, the publication No. 130657/1996 discloses a facsimile which is provided with input means for scanning a document and inputting a color image, transmission means for faxing the color image thus inputted by the input means, special document judging means for judging whether the color image inputted by the input means is a special document, copying of which is prohibited, such as paper money, valuable securities, or the like, and control means for controlling the transmission means to prohibit the transmission of the inputted color image in the case where the judging means judges that the inputted color image is the special document.
However, forgery using the image transmission device should be taken into consideration not only when the scanned image is directly transmitted to a receiver by the facsimile as in the case of the above publication, but also when such an image as to be scanned and temporarily stored in a memory is transmitted by request of an external device (or retrieved from the external device) as in the case of performing polling transmission by facsimile.
More specifically, in the case of the facsimile polling transmission (receiving), image data which are scanned by a transmitter facsimile and temporarily stored in a memory are transmitted (retrieved) to a receiver facsimile in response to a transmission request from the receiver facsimile. In that case, it is feasible that the image data of a specific document are retrieved from the receiver facsimile so as to use it for forgery, that should be taken into consideration accordingly.
Further, in the case of a computer, such as a personal computer connected with a computer network, etc., it is possible in general to transfer image data to a different computer terminal by request thereof. Therefore, it is feasible that forgery is committed by retrieving image data stored in a computer terminal from a different computer terminal. The forgery like this should also be taken into consideration.
Further, recently, there has been introduced a facsimile (network scanner) which is connected to a computer terminal via a computer network and can be operated in response to a request from the computer terminal. In a network environment where this network scanner is introduced, it is possible, for example, to transfer document image data scanned by the network scanner to a predetermined computer terminal in response to a request from a computer terminal on the network, and capture a specific image from a computer terminal on the network by the remote control of the network scanner. Therefore, in this network environment, there is a growing need to monitor transmission of the image data of the specific document from a computer terminal on the network by the remote control of the network scanner.
Further, in such a system that the scanned image data is first stored in an information management device, such as a server, thereafter transferring the image data to an external receiver by request thereof, there is a growing need to monitor transmission of the image data of the specific document at the server's end.
As discussed, it is necessary to monitor transmission of the image data of the specific document in either of an image transmission device which transmits the image data stored in advance to an external receiver by request thereof and an image transmission device which first prepare image data by request of an external receiver, then, transmits the image data to the external receiver when ready. The publication No. 130657/1996 does not disclose an image transmission device having the foregoing arrangement in which the transmission of a special document is prohibited.